Tire having a composition comprising an ethylene-rich elastomer, a peroxide and a specific acrylate derivative

ABSTRACT

A tire comprises a rubber composition based on at least one elastomeric matrix mainly comprising a random copolymer comprising ethylene units and conjugated diene units, the mole fraction of the ethylene units in the copolymer being within a range extending from 50% to 95%; a peroxide; and a specific acrylate derivative.

The invention relates to tyres and more particularly to those in whichthe composition of the tread or that of an inner layer comprises aspecific acrylate derivative and a peroxide.

Tyre layers such as the tread or the inner layers must comply with alarge number of technical, often antinomic, requirements including lowrolling resistance, high wear resistance, good road behaviour, and alsoa good level of cohesion of the material.

Tyre designers are constantly looking for a solution to change theexisting property compromise by improving at least one property of thetyre, without however penalizing others.

It is known that to improve wear resistance a certain stiffness of thetread is desirable, which stiffening of the tread may be obtained forexample by increasing the content of reinforcing filler or byincorporating certain reinforcing resins into the rubber compositionsmaking up these treads. Unfortunately, experience shows that suchstiffening of the tread can decrease, in a known manner, the rollingresistance properties, accompanied by a significant increase inhysteretic losses of the rubber composition. Improving rollingresistance while maintaining acceptable stiffness performance istherefore a problem to be solved for tyre designers.

From the point of view of the rolling resistance, the abovementionedcompromise of properties could be improved thanks to the use of newmixtures having good mechanical properties and a hysteresis as low aspossible in order to be able to use them in the form of rubbercompositions that can be used for the manufacture of varioussemi-finished products used in the composition of tyres. For example,documents WO 2016/102480 and WO 2016/102483 propose to use apolyfunctional acrylate derivative and a peroxide in dieneelastomer-based compositions.

Thus, manufacturers are always looking for solutions to further improverolling resistance without penalizing stiffness.

Continuing its research, the applicant has discovered that the use ofspecific acrylate derivatives in a composition comprising a particularrandom copolymer comprising ethylene units and conjugated diene unitsmakes it possible to improve the rolling resistance and thereinforcement without penalizing the stiffness of the composition.

Thus, a subject of the present invention is in particular a tyrecomprising a rubber composition based on:

-   -   an elastomeric matrix comprising predominantly a random        copolymer comprising ethylene units and conjugated diene units,        the mole fraction of the ethylene units in the copolymer being        within a range extending from 50% to 95%,    -   at least one peroxide, and    -   at least one acrylate derivative of formula (I)

-   -   -   in which:            -   R₁, R₂ and R₃ independently of one another represent a                hydrogen atom or a C₁-C₅ hydrocarbon group selected from                linear, branched or cyclic alkyl groups, aralkyl groups,                alkylaryl groups and aryl groups, and which are                optionally interrupted by one or more heteroatoms, it                being possible for R₂ and R₃ together to form a                non-aromatic ring,            -   R₄ represents a C₁-C₃₀ hydrocarbon group selected from                linear, branched or cyclic alkyl groups, which are                optionally interrupted and/or substituted by one or more                heteroatoms.

I—DEFINITIONS

The expression “composition based on” should be understood as meaning acomposition comprising the mixture and/or the product of the in situreaction of the various constituents used, some of these constituentsbeing able to react and/or being intended to react with one another, atleast partially, during the various phases of manufacture of thecomposition; it thus being possible for the composition to be in thecompletely or partially crosslinked state or in the noncrosslinkedstate.

For the purposes of the present invention, the expression “part byweight per hundred parts by weight of elastomer” (or phr) should beunderstood as meaning the part by weight per hundred parts by weight ofelastomer.

In the present document, unless expressly indicated otherwise, all thepercentages (%) indicated are percentages (%) by weight.

Furthermore, any interval of values denoted by the expression “between aand b” represents the range of values extending from more than “a” toless than “b” (i.e. limits a and b excluded), while any interval ofvalues denoted by the expression “from a to b” means the range of valuesextending from “a” up to “b” (i.e. including the strict limits a and b).In the present document, when an interval of values is described by theexpression “from a to b”, the interval represented by the expression“between a and b” is also and preferably described.

When reference is made to a “predominant” compound, this is understoodto mean, for the purposes of the present invention, that this compoundis predominant among the compounds of the same type in the composition,that is to say that it is the one which represents the greatest amountby weight among the compounds of the same type. Thus, for example, apredominant elastomer is the elastomer representing the greatest weightwith respect to the total weight of the elastomers in the composition.In the same way, a “predominant” filler is that representing thegreatest weight among the fillers of the composition. By way of example,in a system comprising just one elastomer, the latter is predominant forthe purposes of the present invention and, in a system comprising twoelastomers, the predominant elastomer represents more than half of theweight of the elastomers. Preferably, the term “predominant” isunderstood to mean present at more than 50%, preferably more than 60%,70%, 80%, 90%, and more preferentially the “predominant” compoundrepresents 100%.

The compounds comprising carbon mentioned in the description can be offossil origin or biosourced. In the latter case, they can result,partially or completely, from biomass or be obtained from renewablestarting materials resulting from biomass. Polymers, plasticizers,fillers, and the like, are concerned in particular.

II—DESCRIPTION OF THE INVENTION

II-1 Elastomeric matrix

The composition of the tyre according to the invention has the essentialcharacteristic of comprising an elastomeric matrix comprisingpredominantly a random copolymer comprising ethylene units andconjugated diene units (also referred to herein as “the copolymer”), themole fraction of the ethylene units in the copolymer being within arange extending from 50% to 95%.

According to the invention, the conjugated diene units are preferablyselected from the group consisting of butadiene units, isoprene unitsand mixtures of these conjugated diene units. More preferably, theconjugated diene units are predominantly, or even preferentiallyexclusively, butadiene units.

Advantageously, the microstructure of the copolymer is homogeneous. Acopolymer is of homogeneous microstructure when, for each of theseunits, at each instant of polymerization, the concentrations in thechain are identical or virtually identical. Thus, for each of theseunits, at a given instant, the concentration is identical or virtuallyidentical to its concentration at the instant just before and after, andthus at any instant of the polymerization. For the purposes of thepresent invention, in the expression “the concentration is identical orvirtually identical to”, the term “virtually identical” is intended tomean a variation of less than 2 mol %.

In particular, in the random copolymer comprising ethylene units andconjugated diene units, the molar concentration in each of these unitsis constant all along the copolymer chain. Thus, for a representativenumber of successive units defining a segment, present at the beginning,middle or end or at any other place of the chain of the copolymer, theconcentration of ethylene units and conjugated diene units is identicalor virtually identical in each segment. A sequence of 10 units may be arepresentative number.

Advantageously, the concentration of ethylene units and conjugated dieneunits (preferably butadiene units) is identical or virtually identicalall along the copolymer chain. It will be possible to determine theconcentration of each of the units in advance according to the nature ofthe catalytic system selected and to the operating conditions (monomerconcentrations and pressure in particular).

Advantageously, the mole fraction of the ethylene units, in the randomcopolymer comprising ethylene units and conjugated diene units, iswithin a range extending from 60% to 90%, preferably from 65% to 85%.

The mole fraction of conjugated diene units (preferably butadiene units)in the copolymer is less than or equal to 50%. Preferably, it is withina range extending from 5% to 50%, preferably from 10% to 40%, preferablyfrom 15% to 35%.

According to the invention, the random copolymer comprising ethyleneunits and conjugated diene units may comprise trans-1,2-cyclohexaneunits. When the copolymer comprises trans-1,2-cyclohexane units, themole fraction of trans-1,2-cyclohexane units in the copolymer ispreferably between 0% and 25%, preferably from 1% to 10%, morepreferably from 1% to 5%.

According to the invention, the random copolymer comprising ethyleneunits and conjugated diene units may comprise vinylaromatic units. Byway of vinylaromatic unit, the following are suitable for example:styrene, ortho-, meta-, or para-methylstyrene, the commercially soldmixture “vinyl toluene”, para-tert-butylstyrene, methoxystyrenes,chlorostyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene.Advantageously, the random copolymer comprising ethylene units andconjugated diene units does not comprise a vinylaromatic unit.

Advantageously, the random copolymer comprising ethylene units andconjugated diene units has a weight Mn ranging from 20 000 g/mol to 1500 000 g/mol, more preferentially ranging from 60 000 g/mol to 250 000g/mol.

Advantageously also, the random copolymer comprising ethylene units andconjugated diene units has a polydispersity index which is less than2.5. Preferably, the PDI index of said copolymers is less than 2 and,even more preferentially, this PDI index is less than or equal to 1.9.As with the molecular weights Mn, the polydispersity indices PDI weredetermined in the present application by size exclusion chromatography.

Advantageously also, the random copolymer comprising ethylene units andconjugated diene units has a glass transition temperature Tg which isless than 25° C. More specifically, these copolymers may for examplehave a temperature Tg of between −45° C. and −20° C.

Advantageously also, when the random copolymer comprising ethylene unitsand conjugated diene units additionally comprises trans-1,2-cyclohexaneunits, the copolymer has a crystallinity of less than 25%, moreadvantageously less than 15%, and even more advantageously less than10%.

The techniques used for the determination of the mole fractions,molecular weights, glass transition temperatures and crystallinity aredescribed hereinafter in the examples.

The random copolymers comprising ethylene units and conjugated dieneunits that can be used in the context of the present invention may beobtained according to known synthesis methods, in particular thosedescribed in documents EP 1 092 731, EP 1 554 321, EP 1 656 400, EP 1829 901, EP 1 954 705, EP 1 957 506, FR 3 045 612 or FR 3 045 613.

According to the invention, advantageously, the elastomeric matrixcomprises only, as elastomer, the random copolymer comprising ethyleneunits and conjugated diene units.

Alternatively, the elastomeric matrix may also comprise a dieneelastomer other than the random copolymer comprising ethylene units andconjugated diene units (also referred to herein as “the otherelastomer”). The other elastomer, when it is present, is a minority,that is to say that it represents less than 50%, 40%, 30%, 20% or evenless than 10% by weight of the elastomeric matrix.

The other elastomer of the elastomeric matrix of the tyre according tothe invention is preferentially selected from the group of highlyunsaturated diene elastomers consisting of polybutadienes (abbreviatedto “BRs”), synthetic polyisoprenes (IRs), natural rubber (NR), butadienecopolymers, isoprene copolymers and mixtures of these elastomers. Suchcopolymers are more preferentially selected from the group consisting ofbutadiene/styrene copolymers (SBRs), isoprene/butadiene copolymers(BIRs), isoprene/styrene copolymers (SIRs), isoprene/butadiene/styrenecopolymers (SBIRs), butadiene/acrylonitrile copolymers (NBRs),butadiene/styrene/acrylonitrile copolymers (NSBRs) or a mixture of twoor more of these compounds.

II-2 Acrylate Derivative

The tyre according to the invention comprises a composition whichcomprises at least one acrylate derivative of formula (I)

-   -   in which:        -   R₁, R₂ and R₃ independently of one another represent a            hydrogen atom or a C₁-C₈ hydrocarbon group selected from            linear, branched or cyclic alkyl groups, aralkyl groups,            alkylaryl groups and aryl groups, and which are optionally            interrupted by one or more heteroatoms, it being possible            for R₂ and R₃ together to form a non-aromatic ring,        -   R₄ represents a C₁-C₃₀ hydrocarbon group selected from            linear, branched or cyclic alkyl groups, which are            optionally interrupted and/or substituted by one or more            heteroatoms.

Cyclic alkyl group is understood to mean an alkyl group comprising oneor more rings.

Hydrocarbon group or chain interrupted by one or more heteroatoms isunderstood to mean a group or chain comprising one or more heteroatoms,each heteroatom being between two carbon atoms of said group or of saidchain, or between a carbon atom of said group or of said chain andanother heteroatom of said group or of said chain, or between two otherheteroatoms of said group or of said chain.

Hydrocarbon group or chain substituted by one or more heteroatoms isunderstood to mean a group or chain comprising one or more heteroatoms,each heteroatom being bonded to the hydrocarbon group or chain by acovalent bond without interrupting the hydrocarbon group or chain.

When R₄ comprises a cyclic hydrocarbon group, it can be a non-aromaticor aromatic cyclic hydrocarbon group.

The heteroatom(s) of the R₁, R₂, R₃ and R₄ radicals can be oxygen,sulfur, nitrogen, phosphorus or silicon atoms, preferably oxygen ornitrogen atoms.

Preferentially, R₁, R₂ and R₃ independently represent a hydrogen atom, amethyl group or an ethyl group. More preferentially, R₁, R₂ and R₃ caneach represent a hydrogen atom. Alternatively, R₂ and R₃ can eachrepresent a hydrogen atom and R₁ represents a methyl group.

Regardless of the R₁, R₂ and R₃ groups, R₄ advantageously represents alinear or branched C₃-C₃₀, alkyl group, optionally interrupted and/orsubstituted by one or more oxygen or nitrogen atoms, preferably oxygenatoms. More preferably, R₄ represents a linear or branched C₅-C₂₀,preferably C₆-C₁₆, alkyl group, optionally interrupted and/orsubstituted by one or more oxygen or nitrogen atoms, preferably oxygenatoms. According to one advantageous embodiment, R₄ is not interruptedand/or substituted by one or more heteroatoms. According to anotheradvantageous embodiment, R₄ is interrupted and/or substituted by one ormore heteroatoms, preferably one or more oxygen or nitrogen atoms,preferably oxygen atoms.

Advantageously, the acrylate derivative of formula (I) is chosen fromthe group consisting of lauryl (meth)acrylate, stearyl (meth)acrylate,polycaprolactone (meth)acrylate, isophoryl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, 4-acetoxyphenethyl (meth)acrylate,4-acryloylmorpholine, butyl (meth)acrylate, tert-butyl (meth)acrylate,benzyl 2-propyl(meth)acrylate, 2-[[(butylamino)carbonyl]oxy]ethyl(meth)acrylate, 2-carboxyethyl (meth)acrylate, oligo-2-carboxyethyl(meth)acrylate, 2-(diethylamino)ethyl (meth)acrylate, di(ethyleneglycol) ethyl ether (meth)acrylate, 2-(dimethylamino)ethyl(meth)acrylate, 3-(dimethylamino)propyl (meth)acrylate, ethylene glycoldicyclopentenyl (meth)acrylate, ethylene glycol methyl ether(meth)acrylate, ethylene glycol phenyl ether (meth)acrylate,2-ethylhexyl (meth)acrylate, hexyl (meth)acrylate, 4-hydroxybutyl(meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl(meth)acrylate, hydroxypropyl (meth)acrylate, isobornyl (meth)acrylate,isobutyl (meth)acrylate, isodecyl (meth)acrylate, isooctyl(meth)acrylate, octadecyl (meth)acrylate, poly(ethylene glycol) methylether (meth)acrylate, poly(propylene glycol) (meth)acrylate),N-propyl(meth)acrylamide, tetrahydrofurfuryl (meth)acrylate,2-tetrahydropyranyl (meth)acrylate, 3,5,5-trimethylhexyl (meth)acrylate,10-undecenyl (meth)acrylate, ethoxylated nonylphenol (meth)acrylate,propoxylated nonylphenol (meth)acrylate, phenoxyethyl (meth)acrylate,ethoxylated nonylphenol mono(meth)acrylate, propoxylated nonylphenolmono(meth)acrylate, o-phenylphenoxyethyl (meth)acrylate,2-[[butylamino)carbonyl]oxy]ethyl (meth)acrylate,2-(2-ethoxyethoxy)ethyl (meth)acrylate, octyldecyl (meth)acrylate,isodecyl (meth)acrylate, propoxylated neopentyl glycol monomethyl ether(meth)acrylate, tricyclodecane methanol (meth)acrylate and mixturesthereof.

More preferably, the acrylate of formula (I) is selected from the groupconsisting of lauryl acrylate, stearyl acrylate, polycaprolactoneacrylate, isophoryl acrylate, tert-butyl cyclohexyl acrylate,4-acetoxyphenethyl acrylate, 4-acryloylmorpholine, butyl acrylate,tert-butyl acrylate, benzyl 2-propylacrylate,2-[[(butylamino)carbonyl]oxy]ethyl acrylate, 2-carboxyethyl acrylate,oligo-2-carboxyethyl acrylate, 2-(diethylaminoethyl acrylate,di(ethylene glycol) ethyl ether acrylate, 2-(dimethylamino)ethylacrylate, 3-(dimethylamino)propyl acrylate, ethylene glycoldicyclopentenyl acrylate, ethylene glycol methyl ether acrylate,ethylene glycol phenyl ether acrylate, 2-ethylhexyl acrylate, hexylacrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl acrylate,2-hydroxy-3-phenoxypropyl acrylate, hydroxypropyl acrylate, isobornylacrylate, isobutyl acrylate, isodecyl acrylate, isooctyl acrylate,octadecyl acrylate, poly(ethylene glycol) methyl ether acrylate,poly(propylene glycol) acrylate, N-propylacrylamide, tetrahydrofurfurylacrylate, 2-tetrahydropyranyl acrylate, 3,5,5-trimethylhexyl acrylate,10-undecenyl acrylate, ethoxylated nonylphenol acrylate, propoxylatednonylphenol acrylate, phenoxyethyl acrylate, ethoxylated nonylphenolmonoacrylate, propoxylated nonylphenol monoacrylate,o-phenylphenoxyethyl acrylate, 2-[[butylamino)carbonyl]oxy]ethylacrylate, 2-(2-ethoxyethoxy)ethyl acrylate, octyldecyl acrylate,isodecyl acrylate, propoxylated neopentyl glycol monomethyl etheracrylate, tricyclodecane methanol and mixtures thereof.

By way of example of a commercially available acrylate derivative offormula (I), mention may be made of those from Sigma-Aldrich: laurylacrylate (LA); those from Rahn AG under the name Genomer 1117, 1119,1120, 1121, 1122 or under the name Miramer M120, M130, M140, M164, M166,M170; those from IGM Resins, under the name Photomer 4003, 4012, 4035,4039, 4066, 4135, 4141, 4142, 4184, 4211, 4808, 4810, 4812, 8127; orelse those from under the name Sartomer SR217, SR256, SR257C, SR285,SR335, SR336, SR339, SR395, SR410, SR420, SR440, SR484, SR489, SR495B,SR504D, SR506D, SR531, SR586, SR587, SR9075.

In the tyre composition according to the invention, the amount ofacrylate derivative of formula (I), in the composition of the tyreaccording to the invention, is preferably within a range extending from5 to 50 phr, preferably from 5 to 30 phr, preferably from more than 5 to25 phr, preferably from 10 to 25 phr.

II-3 Peroxide

In addition to the elastomeric matrix and the acrylate derivativedescribed above, the rubber composition of the tyre of the inventionuses a peroxide, which may be any peroxide known to those skilled in theart.

Among the peroxides, which are well known to those skilled in the art,it is preferable to use, for the invention, a peroxide selected from thefamily of the organic peroxides. Thus, advantageously, the peroxide isan organic peroxide.

The term “organic peroxide” is understood to mean an organic compound,that is to say a compound containing carbon, comprising an —O—O— group(two oxygen atoms connected by a covalent single bond).

Advantageously, the organic peroxide is selected from the groupconsisting of dialkyl peroxides, monoperoxycarbonates, diacyl peroxides,peroxyketals, peroxyesters and mixtures thereof.

Preferably, the dialkyl peroxides are selected from the group consistingof dicumyl peroxide, di(t-butyl) peroxide, t-butyl cumyl peroxide,2,5-dimethyl-2,5-di(t-butylperoxy)hexane,2,5-dimethyl-2,5-di(t-amylperoxy)hexane,2,5-dimethyl-2,5-di(t-butylperoxy)hex-3-yne,2,5-dimethyl-2,5-di(t-amylperoxy)hex-3-yne,α,α′-di[(t-butylperoxy)isopropyl]benzene,α,α′-di[(t-amylperoxy)isopropyl]benzene, di(t-amyl) peroxide,1,3,5-tri[(t-butylperoxy)isopropyl]benzene,1,3-dimethyl-3-(t-butylperoxy)butanol and1,3-dimethyl-3-(t-amylperoxy)butanol and mixtures thereof.

Some monoperoxycarbonates, such as OO-tert-butyl O-(2-ethylhexyl)monoperoxycarbonate, OO-tert-butyl O-isopropyl monoperoxycarbonate,OO-tert-amyl O-(2-ethylhexyl) monoperoxycarbonate, and mixtures thereof,can also be used.

Among the diacyl peroxides, the preferred peroxide is benzoyl peroxide.

Among the peroxyketals, the preferred peroxides are selected from thegroup consisting of 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane,n-butyl 4,4-di(t-butyl peroxy)valerate, ethyl3,3-di(t-butylperoxy)butyrate, 2,2-di(t-amylperoxy)propane,3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane (or methyl ethylketone peroxide cyclic trimer), 3,3,5,7,7-pentamethyl-1,2,4-trioxepane,n-butyl 4,4-bis(t-amylperoxy)valerate, ethyl3,3-di(t-amylperoxy)butyrate, 1,1-di(t-butylperoxy)cyclohexane,1,1-di(t-amylperoxy)cyclohexane and mixtures thereof.

Preferably, the peroxyesters are selected from the group consisting oftert-butyl peroxybenzoate, tert-butyl peroxy-2-ethylhexanoate,tert-butyl peroxy-3,5,5-trimethylhexanoate and mixtures thereof.

Preferably, the organic peroxide is selected from the group consistingof dicumyl peroxide, aryl or diaryl peroxides, diacetyl peroxide,benzoyl peroxide, dibenzoyl peroxide, di(tert-butyl) peroxide,tert-butyl cumyl peroxide, 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, n-butyl 4,4′-di(tert-butylperoxy)valerate, OO-(t-butyl)O-(2-ethylhexyl) monoperoxycarbonate, tert-butyl peroxyisopropylcarbonate, tert-butyl peroxybenzoate, tert-butylperoxy-3,5,5-trimethylhexanoate,1,3(4)-bis(tert-butylperoxyisopropyl)benzene and their, even morepreferentially from the group consisting of dicumyl peroxide, n-butyl4,4′-di(tert-butylperoxy)valerate, OO-(t-butyl) O-(2-ethylhexyl)monoperoxycarbonate, tert-butyl peroxyisopropyl carbonate, tert-butylperoxybenzoate, tert-butyl peroxy-3,5,5-trimethylhexanoate,1,3(4)-bis(tert-butylperoxyisopropyl)benzene and mixtures thereof.

In the tyre composition according to the invention, the amount ofperoxide is preferably within a range extending from 0.1 to 10 phr. Morepreferentially, the amount of peroxide in the composition is within arange extending from 0.5 to 5 phr, preferably from 1 to 4 phr.

Various packaged products, known under their trade names, are availablecommercially; mention may be made of Dicup from Hercules Powder Co.,Perkadox Y12 from Noury van der Lande, Peroximon F40 from MontecatiniEdison S.p.A., Trigonox from Noury van der Lande, Varox from R. T.Vanderbilt Co. or also Luperko from Wallace & Tiernan Inc.

II-4 Reinforcing Filler

The composition of the tyre according to the invention does not requirea reinforcing filler, which is one of its advantages since this makes itpossible to greatly reduce the hysteresis of the composition, and thusthe rolling resistance of the tyre.

Thus, preferably, the composition of the tyre according to the inventiondoes not comprise a reinforcing filler or comprises less than 160 phrthereof.

Advantageously, the composition of the tyre can comprise from 5 to 120phr, preferably from 5 to 65 phr, preferably from 5 to 60 phr,preferably from 10 to 55 phr, of reinforcing filler, known for itscapacity to reinforce a rubber composition that can be used for themanufacture of tyres.

The reinforcing filler can be an organic filler such as carbon black, aninorganic filler such as silica or else a mixture of these two types offillers.

All carbon blacks, in particular the blacks conventionally used in tyresor their treads, are suitable as carbon blacks. Among the latter,mention will more particularly be made of the reinforcing carbon blacksof the 100, 200 and 300 series, or the blacks of the 500, 600 or 700series (ASTM D-1765-2017 grades), such as, for example, the N115, N134,N234, N326, N330, N339, N347, N375, N550, N683 and N772 blacks. Thesecarbon blacks can be used in the isolated state, as availablecommercially, or in any other form, for example as support for some ofthe rubber additives used. The carbon blacks could, for example, alreadybe incorporated into the diene elastomer, in particular isopreneelastomer, in the form of a masterbatch (see for example applications WO97/36724-A2 or WO 99/16600-A1).

Mention may be made, as an example of organic fillers other than carbonblacks, of functionalized polyvinyl organic fillers, such as describedin applications WO2006/069792-A1, WO2006/069793-A1, WO2008/003434-A1 andWO2008/003435-A1.

The term “reinforcing inorganic filler” should be understood here asmeaning any inorganic or mineral filler, whatever its colour and itsorigin (natural or synthetic), also known as “white filler”, “clearfiller” or even “non-black filler”, in contrast to carbon black, capableof reinforcing, by itself alone, without means other than anintermediate coupling agent, a rubber composition intended for themanufacture of tyres. In a known manner, certain reinforcing inorganicfillers can be characterized in particular by the presence of hydroxylgroups (—OH) on their surface.

Mineral fillers of the siliceous type, preferentially silica (SiO₂), orof the aluminous type, in particular alumina (Al₂O₃), are suitable inparticular as reinforcing inorganic fillers. The silica used can be anyreinforcing silica known to those skilled in the art, in particular anyprecipitated or fumed silica exhibiting a BET specific surface and aCTAB specific surface both of less than 450 m²/g, preferably within arange extending from 30 to 400 m²/g, in particular from 60 to 300 m²/g.

For inorganic fillers such as silica for example, the BET specificsurface area of the inorganic filler is determined by gas adsorptionusing the Brunauer-Emmett-Teller method described in “The Journal of theAmerican Chemical Society”, (Vol. 60, page 309, February 1938), and morespecifically according to a method derived from the standard NF ISO5794-1, appendix E, of June 2010 [multipoint (5 point) volumetricmethod—gas: nitrogen—degassing under vacuum: one hour at 160°C.—relative pressure range p/po: 0.05 to 0.17]. Moreover, the CTABspecific surface area values were determined according to the standardNF ISO 5794-1, appendix G of June 2010. The process is based on theadsorption of CTAB (N-hexadecyl-N,N,N-trimethylammonium bromide) ontothe “outer” surface of the reinforcing filler.

Any type of precipitated silica can be used, in particular highlydispersible precipitated silicas (termed “HDS” for “highly dispersible”or “highly dispersible silica”). These precipitated silicas, which mayor may not be highly dispersible, are well known to those skilled in theart. Mention may be made, for example, of the silicas described inapplications WO 03/016215-A1 and WO 03/016387-A1. Among the commercialHDS silicas, it is possible in particular to use the silicas “Ultrasil®5000GR”, “Ultrasil® 7000GR” from Evonik, the silicas “Zeosil® 1085GR”,“Zeosil® 1115 MP”, “Zeosil® 1165MP”, “Zeosil® Premium 200MP”, “Zeosil®HRS 1200 MP” from Solvay. As non-HDS silica, the following commercialsilicas can be used: “Ultrasil® VN2GR” silicas, “Ultrasil® VN3GR” fromEvonik, the silica “Zeosil® 175GR” from Solvay, the silicas “Hi-SilEZ120G(-D)”, “Hi-Sil EZ160G(-D)”, “Hi-Sil EZ200G(-D)”, “Hi-Sil 243LD”,“Hi-Sil 210”, “Hi-Sil HDP 320G” from PPG.

As other examples of inorganic fillers that can be used in the rubbercompositions of the invention, mention may also be made of mineralfillers of the aluminous type, in particular alumina (Al₂O₃), aluminiumoxides, aluminium hydroxides, aluminosilicates, titanium oxides, siliconcarbides or nitrides, all of the reinforcing type as described forexample in applications WO 99/28376-A2, WO 00/73372-A1, WO 02/053634-A1,WO2004/003067-A1, WO2004/056915-A2, U.S. Pat. No. 6,610,261-B1 and U.S.Pat. No. 6,747,087-B2. Mention may in particular be made of the aluminas“Baikalox A125” or “CR125” (Baikowski company), “APA-100RDX” (Condéa),“Aluminoxid C” (Evonik) or “AKP-G015” (Sumitomo Chemicals).

The physical state in which the reinforcing inorganic filler is providedis not important, whether it is in the form of a powder, of microbeads,of granules, or else of beads or any other appropriate densified form.Of course, reinforcing inorganic filler is also understood to meanmixtures of different reinforcing inorganic fillers, in particular ofsilicas as described above.

Those skilled in the art will understand that, instead of thereinforcing inorganic filler described above, a reinforcing filler ofanother nature could be used, as long as this reinforcing filler ofanother nature is covered with an inorganic layer such as silica, orelse would comprise functional sites, in particular hydroxyls, at itssurface, requiring the use of a coupling agent to establish the bondbetween this reinforcing filler and the diene elastomer. By way ofexample, mention may be made of carbon blacks partially or fully coveredwith silica, or carbon blacks modified with silica, such as, withoutlimitation, the fillers of the “Ecoblack®” type of the “CRX2000” seriesor of the “CRX4000” series from Cabot Corporation.

In order to couple the reinforcing inorganic filler to the dieneelastomer, use may be made, in a well-known way, of an at leastbifunctional coupling agent (or bonding agent) intended to provide asatisfactory connection, of chemical and/or physical nature, between theinorganic filler (surface of its particles) and the diene elastomer. Useis made in particular of organosilanes or polyorganosiloxanes which areat least bifunctional. The term “bifunctional” is understood to mean acompound having a first functional group capable of interacting with theinorganic filler and a second functional group capable of interactingwith the diene elastomer. For example, such a bifunctional compound cancomprise a first functional group comprising a silicon atom, said firstfunctional group being able to interact with the hydroxyl groups of aninorganic filler and a second functional group comprising a sulfur atom,said second functional group being able to interact with the dieneelastomer.

Preferably, the organosilanes are selected from the group consisting oforganosilane polysulfides (symmetrical or asymmetrical) such asbis(3-triethoxysilylpropyl) tetrasulfide, abbreviated to TESPT soldunder the name “Si69” by Evonik or bis(triethoxysilylpropyl)disulfide,abbreviated to TESPD sold under the name “Si75” by Evonik,polyorganosiloxanes, mercaptosilanes, blocked mercaptosilanes, such asS-(3-(triethoxysilyl)propyl) octanethioate sold by Momentive under thename “NXT Silane”. More preferentially, the organosilane is anorganosilane polysulfide.

Of course, use might also be made of mixtures of the coupling agentsdescribed above.

When an inorganic filler is used, the content of coupling agent in thecomposition of the tyre according to the invention is advantageouslyless than or equal to 10 phr, it being understood that it is generallydesirable to use as little as possible thereof. Typically, the contentof coupling agent represents from 0.5% to 15% by weight, with respect tothe amount of reinforcing inorganic filler. Its content is preferablywithin a range extending from 0.5 to 7.5 phr, more preferentially withina range extending from 3 to 3 phr. This content is easily adjusted bythose skilled in the art according to the content of reinforcinginorganic filler used in the composition of the invention.

Preferably, the reinforcing filler of the rubber composition of the tyreaccording to the invention comprises a carbon black, a silica or amixture thereof. Even more preferentially, the reinforcing fillercomprises predominantly carbon black. The reinforcing filler cancomprise, for example, from 50% to 100% by weight of carbon black,preferably from 55% to 90% by weight, preferably from 60% to 80% byweight. Particularly advantageously, the reinforcing filler comprisesexclusively carbon black.

Advantageously, the content of reinforcing filler, preferably thereinforcing filler mainly comprising carbon black, in the composition ofthe tyre according to the invention, is within a range extending from 10to 55 phr, preferably from 15 to 50 phr, preferably 20 to 45 phr.

II-5 Vulcanization System

The composition of the tyre according to the invention does not requirea vulcanization system, which is one of its advantages since this makesit possible to simplify the formulation, and the preparation of thecomposition. If, however, a vulcanization system is present in thecomposition, it is preferably present in small amounts.

The vulcanization system proper is generally based on sulfur (or on asulfur-donating agent) and on a primary vulcanization accelerator.Various known secondary vulcanization accelerators or vulcanizationactivators, such as zinc oxide, stearic acid or equivalent compounds, orguanidine derivatives (in particular diphenylguanidine), are added tothis base vulcanization system, being incorporated during thenon-productive first phase and/or during the productive phase, asdescribed subsequently.

Molecular sulfur (or equivalently molecular sulfur-donating agents),when it is used, is in a content preferentially of less than 0.5 phr.

Thus, very preferentially, the composition does not contain molecularsulfur or sulfur-donating agent as vulcanizing agent or contains lessthan 0.5 phr, preferably less than 0.3 phr, more preferably less than0.1 phr thereof. More preferably, the composition of the tyre accordingto the invention does not contain molecular sulfur or sulfur-donatingagent as vulcanizing agent.

The vulcanization system of the composition according to the inventioncan also comprise one or more additional accelerators, for examplecompounds of the family of the thiurams, zinc dithiocarbamatederivatives, sulfenamides, guanidines or thiophosphates. Use may be madein particular of any compound that is capable of acting as acceleratorof the vulcanization of diene elastomers in the presence of sulfur,notably accelerators of the thiazole type and derivatives thereof, andaccelerators of thiuram or zinc dithiocarbamate type. These acceleratorsare more preferably selected from the group consisting of2-mercaptobenzothiazole disulfide (abbreviated to “MBTS”),N-cyclohexyl-2-benzothiazolesulfenamide (abbreviated to “CBS”),N,N-dicyclohexyl-2-benzothiazolesulfenamide (abbreviated to “DCBS”),N-(tert-butyl)-2-benzothiazolesulfenamide (abbreviated to “TBBS”),N-(tert-butyl)-2-benzothiazolesulfenimide (abbreviated to “TBSI”), zincdibenzyldithiocarbamate (abbreviated to “ZBEC”) and mixtures of thesecompounds. Preferably, use is made of a primary accelerator of thesulfenamide type.

If an accelerator is used, it is used at contents such as those used bythose skilled in the art of vulcanized compositions for tyres.Nevertheless, the composition of the tyre according to the invention ispreferentially devoid of any vulcanization accelerator.

II-6 Other Possible Additives

The rubber compositions of the tyre according to the invention mayoptionally also comprise all or some of the usual additives customarilyused in elastomer compositions for tyres, such as for exampleplasticizers (such as plasticizing oils and/or plasticizing resins),pigments, protective agents such as anti-ozone waxes, chemicalanti-ozonants, antioxidants, anti-fatigue agents, reinforcing resins (asdescribed for example in application WO 02/10269).

Preferably, the composition of the tyre of the invention is devoid ofantioxidant.

According to one preferential mode, the composition of the tyre of theinvention is devoid of plasticizing agent. Alternatively and accordingto an also preferential embodiment, the composition according to theinvention also comprises a plasticizing agent. Preferably, thisplasticizing agent is a solid hydrocarbon resin (or plasticizing resin),an extender oil (or plasticizing oil) or a mixture of the two.

II-7 Tyres

A subject of the present invention is also a finished or semi-finishedrubber article, as well as a tyre, comprising a composition according tothe present invention.

The invention relates in particular to tyres intended to equip motorvehicles of passenger vehicle type, SUVs (“Sport Utility Vehicles”), ortwo-wheel vehicles (notably motorcycles), or aircraft, or elseindustrial vehicles selected from vans, heavy-duty vehicles, i.e.underground trains, buses, heavy road transport vehicles (lorries,tractors, trailers) or off-road vehicles, such as heavy agriculturalvehicles or construction vehicles, and the like.

It is possible to define, within the tyre, three types of regions:

-   -   The radially exterior region in contact with the ambient air,        this region essentially consisting of the tread and of the outer        sidewall of the tyre. An outer sidewall is an elastomeric layer        positioned outside the carcass reinforcement relative to the        inner cavity of the tyre, between the crown and the bead, so as        to completely or partially cover the region of the carcass        reinforcement extending from the crown to the bead.    -   The radially interior region in contact with the inflation gas,        this region generally consisting of the layer airtight to the        inflation gases, sometimes known as interior airtight layer or        inner liner.    -   The internal region of the tyre, that is to say that between the        exterior and interior regions. This region includes layers or        plies which are referred to here as internal layers of the tyre.        These are, for example, carcass plies, tread sublayers, tyre        belt plies or any other layer which is not in contact with the        ambient air or the inflation gas of the tyre.

The composition defined in the present description is particularly wellsuited to the internal layers and to the treads of tyres.

Thus, in the tyre according to the present invention, the compositionmay be present in the tread and/or at least one internal layer of thetyre. According to the invention, the internal layer can be selectedfrom the group consisting of carcass plies, crown plies, bead-wirefillings, crown feet, decoupling layers, edge rubbers, padding rubbers,the tread underlayer and the combinations of these internal layers.Preferably, the internal layer is selected from the group consisting ofcarcass plies, crown plies, bead-wire fillings, crown feet, decouplinglayers and combinations of these internal layers.

The invention relates to the tyres and semi-finished products for tyresdescribed above, articles made of rubber, both in the raw state (that isto say, before curing) and in the cured state (that is to say, aftercrosslinking or vulcanization).

II-8 Preparation of the Rubber Compositions

The rubber composition in accordance with the invention is manufacturedin appropriate mixers using two successive preparation phases well knownto those skilled in the art:

-   -   a first phase of thermomechanical working or kneading        (“non-productive” phase), which can be carried out in a single        thermomechanical step during which all the necessary        constituents, in particular the elastomeric matrix, the optional        fillers and the optional other various additives, with the        exception of the crosslinking system, are introduced into an        appropriate mixer, such as a standard internal mixer (for        example of ‘Banbury’ type). The incorporation of the optional        filler into the elastomer may be performed in one or more        portions while thermomechanically kneading. The non-productive        phase can be carried out at high temperature, up to a maximum        temperature of between 110° C. and 200° C., preferably between        130° C. and 185° C., for a period of time generally of between 2        and 10 minutes.    -   a second phase of mechanical working (“productive” phase), which        is carried out in an external mixer, such as an open mill, after        cooling the mixture obtained during the first non-productive        phase down to a lower temperature, typically of less than 120°        C., for example between 40° C. and 100° C. The crosslinking        system is then incorporated and the combined mixture is then        mixed for a few minutes, for example between 5 and 15 min.

Such phases have been described, for example, in patent applicationsEP-A-0501227, EP-A-0735088, EP-A-0810258, WO 00/05300 or WO 00/05301.

The final composition thus obtained is subsequently calendered, forexample in the form of a sheet or of a plaque, in particular for alaboratory characterization, or also extruded in the form of a rubbersemi-finished (or profiled) element which can be used, for example, as atyre tread or an internal layer for a passenger vehicle. These productscan subsequently be used for the manufacture of tyres, according totechniques known to those skilled in the art.

The composition may be either in the raw state (before crosslinking orvulcanization) or in the cured state (after crosslinking orvulcanization), may be a semi-finished product which can be used in atyre.

The crosslinking of the composition can be carried out in a way known tothose skilled in the art, for example at a temperature of between 130°C. and 200° C., under pressure.

III—EXAMPLES III-1 Measurements and Tests Used Determination of theMolar Masses: Size Exclusion Chromatography Analysis of the Copolymers

-   -   a) For the copolymers which are soluble in tetrahydrofuran (THF)        at ambient temperature, the molar masses were determined by size        exclusion chromatography in THF. The samples were injected using        a Waters 717 injector and a Waters 515 HPLC pump at a flow rate        of 1 ml·min⁻¹ in a series of Polymer Laboratories columns. This        series of columns, placed in a thermostated chamber at 45° C.,        is composed of:        -   1 PL Gel 5 μm precolumn,        -   2 PL Gel 5 μm Mixte C columns,        -   1 PL Gel 5 μm-500 Å column.

The detection was carried out using a Waters 410 refractometer. Themolar masses were determined by universal calibration using polystyrenestandards certified by Polymer Laboratories and a double detection withrefractometer and coupling to the viscometer.

Without being an absolute method, SEC makes it possible to comprehendthe distribution of the molecular weights of a polymer. On the basis ofstandard commercial products of polystyrene type, the variousnumber-average weights (Mn) and weight-average weights (Mw) can bedetermined and the polydispersity index calculated (PDI=Mw/Mn).

-   -   b) For the copolymers which are insoluble in tetrahydrofuran at        ambient temperature, the molar masses were determined in        1,2,4-trichlorobenzene. They were first dissolved under hot        conditions (4 h 00 at 150° C.), then they were injected at 150°        C., with a flow rate of 1 ml·min⁻¹, into a Waters Alliance GPCV        2000 chromatograph equipped with three Styragel columns (2 HT6E        columns and 1 HT2 column). The detection was carried out using a        Waters refractometer. The molar masses were determined by        relative calibration using polystyrene standards certified by        Polymer Laboratories.

Determination of the Mole Fractions

Reference is made to the article “Investigation of ethylene/butadienecopolymers microstructure by ¹H and ¹³C NMR, Llauro M. F., Monnet C.,Barbotin F., Monteil V., Spitz R., Boisson C., Macromolecules 2001, 34,6304-6311”, for a detailed description of the ¹H NMR and ¹³C NMRtechniques which have been specifically used in the present applicationto determine the mole fractions of the ethylene units, the conjugateddiene units and of any trans-1,2-cyclohexane units.

Determination of the Crystallinity

The crystallinity measurement was carried out by comparison of theenthalpy of fusion observed in the case of EBRs. This endothermicphenomenon is observed during the analysis of the thermogram of the DSC(Differential Scanning calorimetry) measurement. The measurement iscarried out by back-and-forth scanning from −150° C. to 200° C. under aninert (helium) atmosphere with a gradient of 20° C./min.

The signal corresponding to the endothermic (fusion) phenomenon isintegrated and the degree of crystallinity is the ratio of the enthalpymeasured to that of the perfectly crystalline polyethylene (290 J/g).

% Crystallinity=(Enthalpy measured in J/g)/(theoretical enthalpy of a100% crystalline polyethylene in J/g).

Determination of the Glass Transition Temperature

The glass transition temperature, Tg, is measured in the presentapplication by the DSC (Differential Scanning calorimetry) technique ona Setaram DSC 131 apparatus. The temperature programme used correspondsto a temperature increase from −120° C. to 150° C. at a rate of 10°C./min. Reference may be made to the method described in application WO2007/054224 (page 11).

Dynamic Properties (after Curing): Tensile Test

These tensile tests make it possible to determine the elasticitystresses and the properties at break. Unless otherwise indicated, theyare carried out in accordance with French Standard NF T 46-002 ofSeptember 1988. Processing the tensile recordings also makes it possibleto plot the curve of modulus as a function of the elongation. Themodulus used here is the nominal (or apparent) secant modulus measuredin first elongation, calculated by reducing to the initial cross sectionof the test specimen. The nominal secant moduli (or apparent stresses,in MPa) are measured in first elongation at 50%, 100% and 300%elongation, respectively denoted M50, M100 and M300.

The tests for elongation at break (% EB) and stress at break (SB) arebased on the standard NF ISO 37 from December 2005 on a dumbbell-shapedtest specimen of H2 type and are measured at a pull speed of 500 mm/min.The elongation at break is expressed as % elongation. The stress atbreak is expressed in MPa.

All these tensile measurements are carried out under the standardconditions of temperature (23±2° C.) and hygrometry (50±5% relativehumidity), according to French Standard NF T 40-101 (December 1979).

The dynamic properties G*(25%) and tan(8)max at 60° C. are measured on aviscosity analyser (Metravib VA4000), according to Standard ASTM D5992-96. The response of a sample of crosslinked composition(cylindrical test specimen with a thickness of 4 mm and a cross sectionof 400 mm²), subjected to a simple alternating sinusoidal shear stress,at a frequency of 10 Hz, under the defined conditions of temperature,for example at 60° C., according to Standard ASTM D 1349-99 or, as thecase may be, at a different temperature, is recorded. A strain amplitudesweep is carried out from 0.1% to 50% (outward cycle) and then from 50%to 1% (return cycle). The results made use of are the complex dynamicshear modulus G* and the loss factor tan(8). The maximum value of tan(8)observed, denoted tan(8)max, and the complex dynamic shear modulus G* at25% strain, at 60° C., are shown for the return cycle.

Rheometry

The measurements are carried out at a given temperature (for example140° C.) with an oscillating disc rheometer, according to Standard DIN53529—Part 3 (June 1983). The change in the rheometric torque, ATorque,as a function of the time describes the change in the stiffening of thecomposition as a result of the vulcanization reaction. The measurementsare processed according to Standard DIN 53529—Part 2 (March 1983): t0 isthe induction period (expressed in min), that is to say the timenecessary for the start of the crosslinking reaction; to (for examplet95) is the time necessary to achieve a conversion of a % (for example95%), that is to say a % (for example 95%) of the difference between theminimum and maximum torques. The lower the value of ta, the more thecomposition will have rapidly crosslinked, that is to say that thecuring will have been rapid.

III-2 Preparation of the Compositions

The tests which follow are carried out in the following way: theelastomer, the reinforcing filler, the acrylate derivative and also thevarious other ingredients, with the exception of the crosslinkingsystem, are successively introduced into a blade mixer (final degree offilling: approximately 70% by volume), the initial vessel temperature ofwhich is approximately 90° C. Thermomechanical working (non-productivephase) is then carried out in one step, which lasts in totalapproximately from 3 to 4 min, until a maximum “dropping” temperature of150° C. is reached.

The mixture thus obtained is recovered and cooled and then thecrosslinking system (peroxide or sulfur as appropriate) is incorporated,on a mixer (homo-finisher) at 23° C. or 50° C., respectively, by mixingthe whole (productive phase) in a cylinder tool for a suitable period oftime (for example between 5 and 12 min).

The compositions thus obtained are subsequently calendered, either inthe form of slabs (thickness of 2 to 3 mm) or of thin sheets of rubberfor the measurement of their physical or mechanical properties, orextruded in the form of a profiled element.

III-3 Tests on Rubber Compositions III-3.1 Effect of the Nature of theCrosslinking System

The object of the examples presented below is in particular to comparethe effect of the replacement of a conventional vulcanization system bya system based on an acrylate derivative and peroxide.

Three rubber compositions were prepared as indicated in point III-2above: a control composition T1 which differs from the composition inaccordance with the invention (C1) by virtue of the nature of thecrosslinking system, and a control composition T2 which differs from thecomposition in accordance with the invention (C1) by the absence of anacrylate derivative in accordance with the invention. The formulationsthereof (in phr) and the properties thereof have been summarized inTable 1 below.

The results for G*25% at 60° C., M300 and tan(6)max are presented in“base 100” relative to the control composition T1. For the G*25% at 60°C. and M300 values, the higher the value, the more the result isimproved. Moreover, the lower the value of tan(6)max at 60° C. base 100,the lower the hysteresis of the composition will be and thus the moreits rolling resistance will be improved.

TABLE 1 T1 T2 C1 EBR (1) 100 100 100 N234 (2) 40 40 40 Peroxide (3) — 44 LA (4) — — 24.1 Sulfur 1 — — CBS (5) 1 — — ZnO (6) 2.5 — — Stearicacid (7) 1 — — t95 at 140° C. (min) 55 23 28.5 G*25% at 60° C. 100 12292 Tan(δ) max 60° C. 100 95 68 M300 100 85 129 (1) Ethylene-butadienecopolymer with 80 mol % of ethylene units prepared according to aprocess for the polymerization of ethylene and butadiene according toExample 4-2 of patent EP 1 954 705 B1 in the name of the Applicants, thepolymerization time being adjusted so as to obtain a molar mass Mn =153000 g/mol with a polydispersity index equal to 1.9 (2) Carbon blackN234 (name according to Standard ASTM D-1765) (3)1,1-Bis(t-butylperoxy)-3,3,5-trimethylcyclohexane (Luperox 231 fromArkema) (4) Lauryl acrylate from Sigma-Aldrich (5)N-Cyclohexyl-2-benzothiazolesulfenamide (Santocure CBS from Flexsys) (6)Zinc oxide (industrial grade - Umicore) (7) Stearin (Pristerene 4931from Uniqema)

These results show that the replacement of a conventional vulcanizationsystem by a crosslinking system based on peroxide and an acrylatederivative in accordance with the invention makes it possible toaccelerate the rate of crosslinking, to improve the rolling resistanceand the reinforcement of the composition, while retaining an acceptablelevel of stiffness for use in a tyre.

III-3.2 Effective the Nature of the Elastomeric Matrix

Other examples were carried out in order to compare the effect of thereplacement of an elastomeric matrix based on natural rubber and onpolybutadiene by a copolymer comprising ethylene units and conjugateddiene units.

A control composition T3 was thus prepared as indicated in point III-2above in order to compare it with the composition in accordance with theinvention (C1) above. Their formulations (in phr) and their propertieshave been summarized in Table 2 below.

The results for CR, G*25% at 60° C. and tan(6)max are presented in “base100” relative to the control composition T3. For the CR and G*25% at 60°C. values, the higher the value, the better the result. Moreover, thelower the value of tan(6)max at 60° C. base 100, the lower thehysteresis of the composition will be and thus the more its rollingresistance will be improved.

TABLE 2 T3 C1 NR (8)  75 — BR (9)  25 — EBR (1) — 100 N234 (2)  40 40Peroxide (3)  4 4 LA (4) — 24.1 CR 100 155 G*25% at 60° C. 100 234Tan(δ) max 60° C. 100 69 (1) to (4): see Table 1 above (8) Naturalrubber (9) Polybutadiene (Nd) with 0.7% of 1,2; 1.7% of trans 1,4; 98%of cis 1,4 (Tg = −105° C.) (Buna CB24 from Arlanxeo)

These results show that the use of acrylate derivatives in accordancewith the invention, in an elastomeric matrix based on a copolymercomprising ethylene units and conjugated diene units, and aperoxide-based crosslinking system, makes it possible to improve themechanical properties, stiffness and rolling resistance compared to acomposition comprising a conventional elastomeric matrix.

1.-15. (canceled)
 16. A tire comprising a rubber composition based on:an elastomeric matrix comprising predominantly a random copolymercomprising ethylene units and conjugated diene units, the mole fractionof the ethylene units in the copolymer being within a range extendingfrom 50% to 95%; at least one peroxide; and at least one acrylatederivative of formula (I)

in which: R₁, R₂ and R₃ independently of one another represent ahydrogen atom or a C₁-C₈ hydrocarbon group selected from linear,branched or cyclic alkyl groups, aralkyl groups, alkylaryl groups andaryl groups, and which are optionally interrupted by one or moreheteroatoms, it being possible for R₂ and R₃ together to form anon-aromatic ring, and R₄ represents a C₁-C₃₀ hydrocarbon group selectedfrom linear, branched or cyclic alkyl groups, which are optionallyinterrupted and/or substituted by one or more heteroatoms.
 17. The tireaccording to claim 16, wherein the conjugated diene units are selectedfrom the group consisting of butadiene units, isoprene units andmixtures thereof.
 18. The tire according to claim 16, wherein the molefraction of the ethylene units in the random copolymer comprisingethylene units and conjugated diene units is within a range extendingfrom 60% to 90%.
 19. The tire according to claim 16, wherein R₁, R₂ andR₃ each represent a hydrogen atom.
 20. The tire according to claim 16,wherein R₁ represents a methyl group, and R₂ and R₃ each represent ahydrogen atom.
 21. The tire according to claim 16, wherein R₄ representsa linear or branched C₃-C₃₀ alkyl group, optionally interrupted and/orsubstituted by one or more oxygen or nitrogen atoms.
 22. The tireaccording to claim 16, wherein the at least one acrylate derivative offormula (I) is selected from the group consisting of lauryl(meth)acrylate, stearyl (meth)acrylate, polycaprolactone (meth)acrylate,isophoryl (meth)acrylate, tert-butyl cyclohexyl (meth)acrylate,4-acetoxyphenethyl (meth)acrylate, 4-acryloylmorpholine, butyl(meth)acrylate, tert-butyl (meth)acrylate, benzyl2-propyl(meth)acrylate, 2-[[(butylamino)carbonyl]oxy]ethyl(meth)acrylate, 2-carboxyethyl (meth)acrylate, oligo-2-carboxyethyl(meth)acrylate, 2-(diethylamino)ethyl (meth)acrylate, di(ethyleneglycol) ethyl ether (meth)acrylate, 2-(dimethylamino)ethyl(meth)acrylate, 3-(dimethylamino)propyl (meth)acrylate, ethylene glycoldicyclopentenyl (meth)acrylate, ethylene glycol methyl ether(meth)acrylate, ethylene glycol phenyl ether (meth)acrylate,2-ethylhexyl (meth)acrylate, hexyl (meth)acrylate, 4-hydroxybutyl(meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl(meth)acrylate, hydroxypropyl (meth)acrylate, isobornyl (meth)acrylate,isobutyl (meth)acrylate, isodecyl (meth)acrylate, isooctyl(meth)acrylate, octadecyl (meth)acrylate, poly(ethylene glycol) methylether (meth)acrylate, poly(propylene glycol) (meth)acrylate,N-propyl(meth)acryl amide, tetrahydrofurfuryl (meth)acrylate,2-tetrahydropyranyl (meth)acrylate, 3,5,5-trimethylhexyl (meth)acrylate,10-undecenyl (meth)acrylate, ethoxylated nonylphenol (meth)acrylate,propoxylated nonylphenol (meth)acrylate, phenoxyethyl (meth)acrylate,ethoxylated nonylphenol mono(meth)acrylate, propoxylated nonylphenolmono(meth)acrylate, o-phenylphenoxyethyl (meth)acrylate,2-[[butylamino)carbonyl]oxy]ethyl (meth)acrylate,2-(2-ethoxyethoxy)ethyl (meth)acrylate, octyldecyl (meth)acrylate,isodecyl (meth)acrylate, propoxylated neopentyl glycol monomethyl ether(meth)acrylate, tricyclodecane methanol (meth)acrylate and mixturesthereof.
 23. The tire according to claim 16, wherein the amount of theat least one acrylate derivative of formula (I) in the rubbercomposition is within a range extending from 5 to 50 parts by weight perhundred parts by weight of elastomer, phr.
 24. The tire according toclaim 16, wherein the at least one peroxide in the rubber composition isan organic peroxide.
 25. The tire according to claim 24, wherein theorganic peroxide is selected from the group consisting of dicumylperoxide, aryl or diaryl peroxides, diacetyl peroxide, benzoyl peroxide,dibenzoyl peroxide, di(tert-butyl peroxide, tert-butyl cumyl peroxide,2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, n-butyl4,4′-di(tert-butylperoxy)valerate, OO-(t-butyl)O-(2-ethylhexyl)monoperoxycarbonate, tert-butyl peroxyisopropylcarbonate, tert-butylperoxybenzoate, tert-butyl peroxy-3,5,5-trimethylhexanoate,1,3(4)-bis(tert-butylperoxyisopropyl)benzene and mixtures thereof. 26.The tire according to claim 16, wherein the amount of the at least oneperoxide in the rubber composition is within a range extending from 0.1to 10 phr.
 27. The tire according to claim 16, wherein the rubbercomposition comprises from 5 to 65 phr of reinforcing filler.
 28. Thetire according to claim 27, wherein the reinforcing filler comprises acarbon black, a silica, or a mixture thereof.
 29. The tire according toclaim 27, wherein the reinforcing filler mainly comprises carbon black.30. The tire according to claim 16, wherein the rubber composition ispresent in the tread, in at least one internal layer, or in both thetread and at least one internal layer of the tire.
 31. The tireaccording to claim 30, wherein the at least one internal layer isselected from the group consisting of carcass plies, crown plies,bead-wire fillings, crown feet, decoupling layers, edge rubbers, paddingrubbers, the tread underlayer and combinations thereof.